Fertilizer plant explosion in West, Texas

A fertilizer plant explosion in a small Texas town Wednesday, April 17, 2013 killed as many as 15 people and injured more than 160 others. The blast left the factory a smoldering ruin and leveled homes and businesses for blocks in every direction.

Firefighters use flashlights early Thursday morning, April 18, 2013 to search a destroyed apartment complex near a fertilizer plant that exploded Wednesday night in West, Texas. The massive explosion killed as many as 15 people and injured more than 160, shaking the ground with the strength of a small earthquake and leveling homes and businesses for blocks in every direction. (AP Photo/LM Otero)

Firefighters conduct search and rescue of an apartment destroyed by an explosion at a fertilizer plant in West, Texas, Thursday, April 18, 2013. A massive explosion at the West Fertilizer Co. killed as many as 15 people and injured more than 160, officials said overnight. (AP Photo/LM Otero)

A destroyed car sits as firefighters conduct a search and rescue of an apartment complex destroyed by an explosion at a fertilizer plant in West, Texas, Thursday, April 18, 2013. A massive explosion at the West Fertilizer Co. killed as many as 15 people and injured more than 160, officials said overnight. (AP Photo/LM Otero)

A firefighter stands on a rail line and surveys the remains of a fertilizer plant destroyed by an explosion in West, Texas, Thursday, April 18, 2013. A massive explosion at the West Fertilizer Co. killed as many as 15 people and injured more than 160, officials said overnight. (AP Photo/LM Otero)

The remains of the the West Fertilizer Co. plant smolder in the rain on Thursday, April 18, 2013, in West, Texas. A massive explosion at the plant killed as many as 15 people and injured more than 160, officials said overnight. (AP Photo/Houston Chronicle, Smiley N. Pool)

The front of an apartment complex is destroyed by an explosion at a nearby fertilizer plant in West, Texas, Thursday, April 18, 2013. A massive explosion at the West Fertilizer Co. killed as many as 15 people and injured more than 160, officials said overnight. The explosion that struck around 8 p.m. Wednesday, sent flames shooting into the night sky and rained burning embers and debris down on shocked and frightened residents. (AP Photo/LM Otero)

Official: Several injured in Texas plant explosion. A high school football field is being used as a triage area for victims, authorities said. (Photo Courtesy of KGTV, Ch. 10, San Diego, CA http://www.10news.com/)

Maria Galvan looks for damage to merchandise inside the West Thrift Shop in West, Texas on Thursday, April 18, 2013. A massive explosion at the West Fertilizer Co. killed as many as 15 people and injured more than 160, officials said overnight. The explosion that struck around 8 p.m. Wednesday, sent flames shooting into the night sky and rained burning embers and debris down on shocked and frightened residents. (AP Photo/The Fort Worth Star-Telegram, Paul Moseley)

Gov. Rick Perry, center, speaks during a news conference updating information about the state's emergency response to the explosion and fires in West, Texas, Thursday, April 18, 2013, in Austin, Texas. A massive explosion at the West Fertilizer Co. killed as many as 15 people and injured more than 160, officials said overnight. The explosion that struck around 8 p.m. Wednesday, sent flames shooting into the night sky and rained burning embers and debris down on shocked and frightened residents. (AP Photo/Eric Gay)